1. Field of the Invention
This invention relates generally to aeration equipment for introducing gas bubbles into aeration basins. More particularly this invention relates to disc type diffusers utilizing flexible membranes thereon and to techniques for securing the membrane to the disc body of the diffuser.
2. Description of the Prior Art
Diffusers for aeration basins are typically mounted to piping carrying air under pressure and function to generate small bubbles in a basin, tank or reservoir to enhance the transfer of oxygen in the reservoir. Flexible membrane diffusers have recently come into prominence due to their ability to generate fine bubbles and improve the overall efficiency of the system. A prior art diffuser of this type employs a disc shaped base fitted to the piping and a flexible membrane mounted to the base. This mounting has taken the form of either a band around the edge of the disc, trapping the membrane against the edge, or by permanently vulcanizing the membrane to the peripheral edge of the disc. (An example of the band attachment method is illustrated in U.S. Pat. No. 4,764,314). If the membrane is not securely attached it will release from the disc when air pressure is applied. Unfortunately, even when the membrane is attached according to these prior art methods, it will occasionally rupture or dislodge during operation, especially if excess air or increased pressure is applied, and the cost of repair or replacement is quite high. Even where the membrane does not release, it will tend to stretch during use and will eventually fail to lay flat against the disc; this allows sludge to accumulate under the membrane and interferes with the operation.